Skewed Field Tiles Near a Ridge

Field tiles immediately adjacent ridge tiles on concrete and clay tile roofs are sometimes skewed. Typically, the bottom edge of these tiles are slightly lifted, and the affected tile are thus not perfectly aligned with adjacent tiles. These tiles are typically sawcut at an upper corner during installation, in order to fit them next to the diagonal ridge. The are then usually mortared into place along with the adjacent ridge tile. These tiles are often still rigidly adhered by the roof mortar. The conditions described above indicate an installation issue. The reason this happens is the lack of or change in support provided to the top of the affected tile. In the middle of the field of the roof, the tiles are all aligned, and supported at their top by the roof deck or furring strips. The bottom edge of such tiles are all bearing on similar conditions provided the top of the tiles below. However, if a tile needs to be cut in order to be placed near a ridge, this changes the bearing condition, or length to the top of the tile, and thus the installed angle of the tile is increased. This is particularly true where the entire width of the tile is diagonally cut.

The field tile visible near the center of the photograph below was not loose, but held rigid by the mortar securing the ridge tiles above. Also, none of the adjacent tiles or mortar displaced or damaged. This condition was consistent with the installation issue described above.

The photograph below shows a tile portion canted clockwise. This portion of tile was also held rigidly by the adjacent ridge tile mortar: